Dept. of Energy extracts fuel from the sea floor

Methane taken from the seabed, replaced by carbon dioxide.

Today, the US Department of Energy announced it had successfully completed a test project that extracted a usable fuel (methane) from its resting place in ocean sediments. The test, performed in conjunction with ConocoPhillips and a Japanese team, could potentially point the way toward a vast new supply of energy. And by linking the extraction with carbon sequestration, the DOE might have found a way to add more hydrocarbons to the world's energy budget without exacerbating climate change.

The material in question is methane hydrates (also called clathrates). These form at high pressure in water, which forms a cage-like structure around pockets of methane. Although these remain solid even above the freezing point of water, changes in pressure and temperature can melt them, releasing methane and returning the water to a liquid state. Clathrate deposits are estimated to be massive. If they can be extracted successfully, they would add a significant boost to the world's hydrocarbon reserves.

The recently completed project, which took place off the coast of Alaska, is a test to determine if we can do that. The extraction technique involves lowering the pressure at the site of the deposit, allowing the methane to escape. At the same time, liquid CO2 was pumped in to occupy the space that held the clathrate. At the pressures prevalent at the site, the CO2 should remain liquid.

There are some big questions that will require followup work—does the process release methane that escapes into the atmosphere? Does the CO2 remain in place long enough that we can consider it sequestered? To get answers to those questions, the DOE has allocated another $6.5 million to further tests, and is requesting $5 million in next year's budget.